<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initialscale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="js/jquery.min.js"></script>
    <title>Document</title>
    <script>
        //ajax 提交
        function mysub(){
            // 1. 判空
            var username=jQuery("#username");
            var password=jQuery("#password");
            if(jQuery.trim(username.val())==""){
                alert("请先输入用户名");
                username.focus();//光标重置到此元素
                return;
            }

            if(jQuery.trim(password.val())==""){
                alert("请先输入密码");
                passworde.focus();//光标重置到此元素
                return;
            }
            jQuery.ajax({
                url:"/user/login4",
                type:"POST",
                data:{"username":username.val(),
            "password":password.val()},
                success:function(result){
                    alert(JSON.stringify(result));
                }
            });


        }

    </script>
</head>
<body>
<div style="text-align: center;">
    <h1>登录</h1>
    ⽤户：<input id="username">
    <br>
    密码：<input id="password" type="password">
    <br>
    <input type="button" value=" 提交 " onclick="mysub()"  style="margin-top: 20px;margin-left: 50px;">
</div>
</body>
</html>